Ferrous metal article and method of producing same



Patented Mar. 18, 1941 FERROUS METAL ARTICLE AND METHOD OF PRODUCING SAME Joseph S. Adelson, Shaker Heights, Ohio, assignor,

by mesne assignments, -to Republic Steel Corporation, Cleveland, Ohio,

Jersey a corporation of New No Drawing. Application March- 27, 1939, Serial No. 264,483 I 10 Claims.

This invention relates to the art of making ferrous metal articles, and is particularly concerned with articles, such as tube and pipe, which are composed of the less expensive steel compositions 5 and yet possess new and improved physical properties, and is also concerned with'a new and improved method for producing such articles.

The physical properties obtained in ferrous metal articles heretofore were determined largely by the, size and composition of the articles. For example, a steel composition was usually selected which would give the desired physical properties in an article of given dimensions. Where the physical properties desired were higher than those obtainable with an inexpensive steel composition within the specified dimensions, a more expensive composition was usually employed, i. e., one containing one or more alloying ingredients which would give to the steel the higher properties desired. For some time the tendency has been to demand higher and higher physical properties and, as a result, more and more expensive compositions have been used in producing such articles, and this tendency has been 25 particularly noticeable in the tube and pipe field.

Since the cost of the steel used is a large part of the cost of the article, the use of the more expensive steel compositions has considerably increased the cost of manufacture of the articles,

30 and this has been especially true in the tube and pipe field where the demand for higher physical properties has been pronounced.

The present invention aims to use the less ex- P pensive steel compositions and yet to produce articles made therefrom which will have improved physical properties corresponding to those of articles having greater dimensions or composed of more expensive steel compositions. Briefly,

I attain these objects by selecting a ferrous metal 40 composition having physical properties which, in

an article of the desired dimensions or in an article of thinner wall thickness, will be somewhat lower than those required in the article and then,

4 by suitably cold working and heat treating the metal, improving the physical properties so that The present invention is applicable to ferrous metal of many different compositions. For example, it is applicable to the class of steels known as simple or low carbon steels, which class is illustrated by the steel which is known commer- 5 cially as S'AE-1020 and which contains between about .15% and about .25% of carbon, and between about .30% and about .60% of manganese, the remainder being iron with the usual amounts of ordinary impurities. It is also applicable to 10 the class of steels known generally as alloy steels. This class includes steels containing between about .10% and about .35% of carbon, between about .30% and about 1.5% of manganese, one ormore of the metals copper, chromium and 15 nickel in amounts up to about 1.5% and/or molybdenum up to about .40%, the remainder of the composition being iron with the usual amounts of ordinary impurities. It will be understood that when more than one of these ad- 20 ditional metals are present, the total amount of such metals should not exceed about 1.5%. It is also applicable to steels whose compositions lie between the two foregoing classes.

The present invention is also applicable to steels containing carbon in excess of about 35% for uses where. improved yield. points and tensile strengths are desired, and where somewhat decreased ductility and increased hardness and. brittleness are not detrimental.

The present process consists, as indicated above, of the two major steps of cold' working and heat treating. The cold working step may be carried out on the metal when it is in hot rolled, or cold rolled and annealed, strip form, as by cold rolling the strip before it is formed into an article of the desired shape, for exampie 8. tube or pipe; or the-hot rolled, or cold rolled and annealed, strip may be formed into an article, such as a tube or pipe, and welded 40 and then cold worked to the desired extent, as by cold drawing the article; or the hot rolled strip may be cold worked by rolling and the article made therefrom may be further cold worked if desired, .as by drawing.

- In making tube or pipe by this invention, any standard method of welding may be employed but, since the electric resistance butt welding method is rapid, economical and comparatively inexpensive, I prefer to employ that method.

, The second major step of the process, that is the heat treating of the article composed of cold worked metal, may be carried out by heating the article at a temperature of between about 500 F. and between about 850 F., for a length of time I have found that when the steel is cold worked I to an extent equivalent to a cold reduction in thickness of between about 10% and about 25%, and is thereafter heat treated, as described, the yield point may be increased from about 10% to about 25%, the tensile strength may be increased from about 5% to about 20% and the increase in elongation in 2" may amount to as much as about 50%.

The following examples are illustrative of the results obtainable by use of the present process:

Cold rolled, annealed, 21 gage, SAE-1020, strip steel containing about .20% of carbon, about .50% of manganese, the remainder being iron with the usual amounts of ordinary impurities was formed and electric resistance butt Welded into a tube 1 in outside diameter. This strip might be considered as being a soft strip because it was annealed after cold rolling which had the effect of reducing or largely eliminating the increase in physical properties which had been given to it by the cold rolling operation. The welded tube was cold drawn to 1" O. D., which cold worked it in an amount equivalent to a cold reduction in thickness of between about 10% and about 25%, and then the tube was heated at about 750 F. for about 2 minutes and allowed to cool in the air. The physical properties of the resulting tube, after welding, after drawing and after heat treatment are set out in the following table:

litlilitiiimu rrj .lvlinilmutm Minimutm 7 yie pom ensi e s r. percen Common when m Sted lb. per sq. in. lb. per sq. in. elong. in 2" of metal of metal of metal As welded 50, 000 60, 000 25 After drawing 60, 000 70, 000 15 After heat treatment. 70,000 80, 000 15 ample. The results in the as welded and heat treated conditions were as follows:

- Yield point Tensile str. Elongation Treatment lbs. per sq. in. lbs. per sq. in. in 2-perof metal oimetal cent of metal Another steel containing about .18% of carbon, about 1.00% of manganese and about. of copper, the remainder being iron with ordinary amounts of the usual impurities was cold rolled to 18, 19, 20 and 21 gage and annealed.

These strips were then cold formed into tube blanks with longitudinal seam edges which were electric resistance butt welded to make tubes of difierent outside diameters. These tubes were cold drawn to smaller diameters and were then heat treated at about 750? F. The following results were obtained from such tubes in the drawn and heat treated conditions:

Yield point Tensile str. Percent Condition when tested lb. per sq. in. lb. per sq. in. elon of metal, of metal in 2 134" 18 gage drawn to 1%"x l8 gage 65,800 75,000 19 After heat treatment 75, 700 79, 600 19 1%" x 19 gage drawn to 1% x 19 gage 07, 200 77, 900 18 After heat treatment 76, 000 83, 200 20 1% x 20 gagedrawn to l" x 20 gage 68, 800 79, 500 18 After heat treatment 75, 400 84, 500 17 1% x 21 gage drawn to 1" x gage 73, 80, 500 17 After heat treatment 600 86, 800 17 I have found that the cold working which takes place during the forming of steel from sheet orstrip into tube or pipe blanks, preliminary to welding, is suflicient to give improved physical properties when heat treated according to this invention. In other words, steel which has been cold rolled and box anneal-ed, may be improved by cold forming the metal into tube or pipe blanks and heat treating it as herein specified after the heat treated at about 750 F. as above described,

with the following results:

- Yield point Tensile str. Size Treatment lbs. per sq. in. lbs. per sq. in.

. of metal of metal Strip 33, 500 58, 200 As welded... 55, 550 00, 900 750 59, 400 67, 600

Strip 38, 500 62, 800 As welded... 59, 100 62, 000 750 69, 800 67, 800

rip 38, 600 62. 200 As welded.-- 57, 800 63, 900 63, 100 72, 500

rip 37, 200 61, 300 As welded. 60, 000 '65, 600 50 65, 500 73, 100

welded into tubes three inches in outside diameter. The .following table gives the proper-. ties of such tubes as welded and after being heat treated at 750 F. as described hereinabove:

' Yield point Tensile s'tr. Elongation Treatment lbs. per sq. in., lbs. per sq. in.. in 2", perof metal oi metal cent As weldedi as, 080 88, 100 :7 750 F 88, 890 99,000 37 As welded 89, 520 93, 840 26 F 93, 320 102, 500 34 Having thus described the present invention so that those skilled in the art may be able to understand and practice the same, I state that what I desire to secure by Letters Patent is defined in what is claimed.

What is claimed is:

1. The method oi. maldng a steel article having improved physical properties which comprises the steps of making an article composed 01' a pearlitic steel containing from about .10% to about .35% of carbon which has been cold worked to anlextentequivalent to a cold reduction of its thickness of between at least 10% and about 50%, and heating an article composed of such cold worked metal at a temperature between about 500 F., and about 850 F.,. for a length of time equal to about one minute for each & to 4, in wall thickness of said article.

2. The method of making a steel article having improved physical properties which comprises the steps of cold working a pearlitic steel containing from about .10% to about .35% of carbon and thereby reducing its thickness between at least and about 50%, converting 'the cold rolled steel into an article, and heat treating said article at a temperature between about 500 F., and about 850 F., for a length of time equal to about one minute for each 2& t0 & of wall thickness of said article.

3. The method of making a steel article having improved physical propertieswhich comprises i the steps of cold rolling a pearlitic steel containing from about .10% to about .35% of carbon, annealing the cold rolled steel, converting the steel into an article, heating the article at a temperature between about 500 F., and about 850 F., for a length of timeequal to one minute for each to 6 in wall thickness of the article, and between the annealing and heating steps cold working the metal to an extent equivalent to a cold reduction in thickness 01 the metal a 'of between at least 10% and about 50%. 40

insheet or strip form and containing'from about .10% to about .35% of carbon and making it into a welded tubular article, heating said article at a temperature between about 500 F., and about 850 F., for a length of time equal to one minute for each to 4 in wall thickness 01' said tube, and cold working the metal so that when it is subjected to said heating step it is in a condition equivalent to that produced by a cold reduction in thickness of between at least 10% and about 50%.

' 5. The method of making a tubular steel article having improved physical properties which comprises the steps of cold working pearlitic steel in sheet or strip form and containing from about .10% to about .35% of carbon to an extent equivalent to a cold reduction in its thickness of between at least 10% and about 50%, making a welded tubular article from such metal, and heating said welded article at a temperature between about 500 F., and about 850 F., for a length of time equal to one minute for each &

to in wall thickness thereof.

6. The method of making a tubular steel article having improved physical properties which comprises the steps of cold forming pearlitic steel in strip or sheet form and containing from about .10% to about 35% of carbon into a tubular blank having longitudinal seam edges and thereby cold working it to an extent equivalent to a cold reduction in wall thickness of between atleast 10% and about 50%, welding said edges together to make a tubular article, and heating said welded article at a temperature between about 500 F., and about 850 F., for a length of time equal to one minute for each to E4 in wall thickness.

'I. The method of making a tubular steel article having improved physical properties which includes the steps of cold rolling pearlitic steel in sheet or strip form and containing from about .10% to about 35% of carbon and forming said meal into tubular shape with longitudinal seam edges, the rolling and forming steps cold working the metal to an extent equivalent to a cold reduction in its wall thickness of between at least 10% and about 50%, welding said edges together, and heating said welded tube at a temperature between about 650 F. and about 850 F.

for a length of time equal to one minute for each 4 in wall thickness thereof.

8. The method of making a tubular steel articlehaving improved physical properties which comprises the steps of cold rolling pearlitic steel in sheet or strip form and containing from about .10% to about 35% of carbon, annealing such cold rolled steel, forming such annealed steel into a tubular blank having longitudinal seam edges and thereby cold working said annealed steel to an extent equivalent to a cold reduction in thickness of between at least 10% and about 50%, welding said edges together to form a welded tubular article, and I heating said article at a temperature between about 500 F. and 850- F. for a length of time equal to one minute for each & to in wall thickness thereof 9. The method of making a tubular steel article having improved physical properties which comprises the steps of cold rolling pearlitic steel in sheet or strip form and containing from about .10% to about 35% of carbon, annealing such cold rolled steel, forming such annealed steel edges, welding said edges together to form a tubular article, cold drawing said welded article and thereby cold working it to an extent equivalent to a cold reduction in its wall thickness of between at least 10% and about and heating the drawn article at ,a temperature of between about 500 F. and about 850 F. for a length of time equal to one minute to each & to in wall thickness thereof. 10. The method of making steel tube or pipe having improved physical properties which comprises the steps of working pearlitic sheet or strip steel containing from about .10% to about .35% of carbon and making it into a welded tubular article, cold drawing said article and thereby reducing its wall thickness between at least 10% and about 50%, and heating such drawn article at a temperature between about 500 F., and about 850 F., for a length of time equal to one minute for each 6, to a in wall thiclmess of said tube.

JOSEPH S. ADELSON. 

